Wireless communication systems confront more and more challenges. One such challenge exists in hot-spots where highly concentrated groups of mobile users create large demands of system capacity. Other challenges exist where co-located heterogeneous networks in certain areas create interference and difficulties in inter-network handover. In order to address these and other problems, various techniques have been developed, such as relay techniques and coordinated multi-point (CoMP) transmission. Both the relay and the CoMP techniques are used to increase the number of parallel channels between the source of a signal and the destination. While these techniques increase system performance, they also require careful network planning and require high computation resources. In some instances, the techniques operate by exploiting additional resources from propagation channels.
Other techniques, such as equalization techniques achieve the same purposes without changing current system configurations. Equalization techniques are used in the receivers of the system in order to recover the original transmitted signal by removing any distortions that arise in the transmittal. When the impact of a channel is perfectly equalized, the signals arriving at the receiver from the different paths are then “aligned” in phases and can be added constructively. Typical examples of equalization techniques include the following: (1) RAKE receiving technique, which equalizes the channel in the delay domain; (2) the frequency equalization technique which has been widely adopted in the receivers based on OFDM transmission; and (3) the time-frequency equalization technique used in the receivers of 4G systems, such as the TD-Long-Term-Evolution (LTE) wireless communication systems.
One problem with these techniques, however is that they require that channel equalization be performed at the receiver, meaning that the receiver have additional resources in order to perform the equalization.